1. Field of the Invention
The present invention relates to a rack bar supporting device of a vehicle steering apparatus. More particularly, the present invention relates to a rack bar supporting device of a rack-and-pinion type steering apparatus of a vehicle, which is configured to be capable of keeping a clearance between a rack bar and a support yoke always constant when the vehicle steering apparatus is operated, so that operational friction and noise can be reduced, the supporting force of the support yoke and the rack bar can be kept constant for a long time, and the driver's steering feeling can be improved.
2. Description of the Prior Art
As generally known in the art, a steering apparatus of a vehicle means an apparatus that allows a driver to change a driving direction of the vehicle by his/her will. The steering apparatus helps the driver to optionally change the center of rotation, about which the vehicle's front wheels are turned, so as to make the vehicle move in a direction desired by the driver.
FIG. 1 is a schematic view of a conventional rack-and-pinion type steering apparatus.
As illustrated, the conventional rack-and-pinion type steering apparatus includes: a steering wheel 100 arranged at a driver's seat side; a steering shaft 105 connected to the steering wheel 100; a steering column 103 configured to allow the steering shaft 100 to be fixed to a vehicle body; a gear box 130 provided with a rack gear 110 and a pinion gear 120 to convert a turning force input from the steering shaft 105 into a rectilinear movement; a rack bar 140 provided with an inner ball joint 135 at each end thereof; a rack housing 170 assembled with the rack bar 140; and a tie rod 150 integrally formed with a ball of the inner ball joint 135.
The tie rod 150 is connected with an outer ball joint 155 and transmits a force to a knuckle 159 to steer tires 158.
FIG. 2 is a cross-sectional view of a conventional rack bar supporting device.
As illustrated, the conventional rack bar supporting device includes a pinion gear 120, a rack bar 140, a support yoke 260, an elastic support 263, and a yoke plug 265. As described above, the rack-and-pinion type gear box 130 is adapted to convert a turning force input from a steering shaft (not shown) into a rectilinear movement.
The rack bar 140 is engaged with the pinion gear 120 to convert a turning movement into a rectilinear movement, in which a device for supporting the rack bar 140 in relation to the pinion gear 120 side is provided behind the rack bar 140 so as to facilitate the engagement between the rack bar 140 and the pinion gear 120.
The device for supporting the rack bar 140 includes a support yoke 260, an elastic support 263, and a yoke plug 265, in which the support yoke 260 is positioned opposite to the rear side of the rack bar 140, on which the rack gear 110 (see FIG. 1) is formed, and is inserted into a cylinder 250 of the gear box 130 to be movable forward and backward perpendicularly to the rack bar 140.
The support yoke 260 is formed in a cylindrical shape so that it can be slid forward and backward, and on the front side thereof where the support yoke 260 is in contact with the rack bar 140, the support yoke 260 is formed with a groove of a semicircular cross-section, so that the front side of the support yoke 260 can be in close contact with the rear side of the rack bar 140.
In addition, in order to assure that the rack bar 140 and the pinion gear 120 can be in close contact with each other to efficiently transmit a force, the elastic support 263 is arranged behind the support yoke 260 to push the support yoke 260 with a predetermined pressure so as to compensate for a clearance produced between the rack bar 140 and the pinion gear 120.
The support yoke 260 is caused to be frictionally slid against the rear side of the rack bar 140. In order to prevent the rack bar 140 from being worn or producing a noise due to friction, the support yoke 260 formed of a plastic material softer than the rack bar 140 may be occasionally used.
The elastic support 263 received in an elastic support groove 220 serves to apply pressure so that the support yoke 260 comes into close contact with the rack bar 140. Typically, a coil spring is employed as the elastic support 263, and the yoke plug 265 is positioned behind the elastic support 263 to support the elastic support 263.
The yoke plug 265 supports the elastic support 263, so that the elastic support 263 can apply pressure to the support yoke 260. Since the yoke plug 265 is typically formed with peaks and valleys of threads so that the yoke plug 265 can be fixedly engaged with the gear box 130 and a lock nut 240, which are formed with peaks and valleys of threads corresponding to those of the yoke plug 265. In addition, a tool groove 230 is formed on the rear side of the yoke plug 265, in which a wrench may be inserted into the tool groove 230.
However, such a conventional rack bar supporting device has problems in that since the support yoke may be greatly worn, operational friction and noise are increased, and a large clearance is produced due to the increased wear of the support yoke, thereby reducing the supporting force of the rack bar, and deteriorating the driver's steering feeling.